tools build: Allow deferring printing the results of feature detection

By setting FEATURE_DISPLAY_DEFERRED=1 a tool may ask for the printout
of the detected features in tools/build/Makefile.feature to be done
later adter extra feature checks are done that are tool specific.

The perf tool will do it via its tools/perf/Makefile.config, as it
performs such extra feature checks.

Acked-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>